DE1187009B - Screw extrusion press for processing thermoplastics or similar materials - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

Number:
File number:
Registration date:
Display day:

B29f

German Kl .: 39 A4 3/00

1187009
A27057X / 39a4
April 30, 1957
February 11, 1965

The invention relates to a screw extruder for processing thermoplastics or similar masses with a for Purposes of continuous conveying, plasticizing and ejecting rotatable screw.

In the case of extrusion, the plastic fed in through a feed hopper is usually combined in one Cylinder plasticized by the supply of heat and by means of a screw through a nozzle or through a Special tool in the form of a hose or a strand with any profile continuously extruded into the open, where depending on the respective requirements a more or less extensive Post-treatment takes place.

The performance of the screw extruder and the quality of the mass strand produced depend heavily on the number and intensity of the movements imposed on the mass within the cylinder. The intensity the known directions of movement can be achieved by common measures such. B. by Change in volume compression in the worm threads by changing the gap between the screw and the inner wall of the cylinder, influenced by various screw head designs, etc. will. Even if minor improvements can be achieved through these measures, so it is not possible to achieve an optimal plasticization up to the complete homogeneity of the material to be processed Bring about mass. This means that beyond certain molecular properties of the mass no more satisfactory quality and no satisfactory services can be achieved and that certain thermoplastics not sufficiently beyond the rubber-elastic state in the plastic or viscous state can be brought into the alone the best possible deformation is guaranteed during the course of the procedure.

In the production of pipes, hoses or any profiles, for example from non-plasticized or plasticized polyvinyl chloride, homogeneous compression, intensive kneading and the generation of high internal shear forces in the mass to be processed are necessary prerequisites in order to obtain a high-quality end product. Rolling mills, internal mixers, plasticizers and similar devices have therefore already been connected upstream of the screw extrusion presses. These devices, as well as screw extruders with very long screws, for example a ratio of length to diameter of the screw of 20: 1, are screw extruders for processing
of thermoplastics or
similar masses

Applicant:

ANKERWERK Gebr. Goller,

Nuremberg, Rennweg 37

but not able to properly convey, plasticize and homogenize all types of material and to supply the required heat to the mass in the cylinder.

The requirements resulting from these findings are now met by the requirements embodied in accordance with the invention Screw extrusion press while avoiding the aforementioned disadvantages. It is therefore in a screw extruder of the type described at the outset, one of the screws is independent of whose rotary motion a pulsating axial motion (axial vibration) forcing a drive device provided, which is adjustable so that the frequency and amplitude of this axial movement the respective Conditions of the extrusion plant are adaptable.

It is already a machine for performing kneading and mixing processes in continuous Work became known, which has a conical screw press and in which the housing the press screw can slide back and forth. The axial reciprocation of the conical screw press surrounding conical housing is to be used in this known machine to by continuously changing the gap between the screw flight and the inner wall of the housing, an intermittent one The plastic flows back into the previous passage and thus a special kneading and to achieve a mixing effect.

However, the mode of operation of this machine is not the same as that of the screw extruder according to the invention comparable, since not intended with the machine designed as a kneading and mixing device is, pulsating axial movements (vibrations) for the purpose of generating high internal To generate shear forces within the mass to be processed.

A mixing and kneading machine has also become known, in whose screw housing a screw is rotatably and axially displaceable. While

509 508/339

of the work process, the rotational movement of the screw conveying in the axial direction is now and foregoing longitudinal movement superimposed in such a way that the recesses of the divided into individual wings Screw flight during the revolution along a helical line around the one on the inner wall The kneading teeth attached to the snail shell wander around. Because of this strange movement the drawn-in mass should be divided into numerous and constantly changing strands, kneaded, mixed and be promoted.

However, the mode of operation of this mixing and kneading machine is not the same as that of a screw extruder comparable, since first of all the rotation and the axial movement of the screw cannot be adapted to the particular circumstances of an extrusion plant and thus a optimal melting of the plastic for the production of strands of the best quality not achieved will. In addition, the structural design of the mixing and kneading machine makes any Superimposition of rotary and axial movements made impossible that the recesses the screw flights always have the kneading teeth attached to the inner wall at a certain point in time have to pass, d. that is, the speed of the screw rotation is proportional to the speed the screw axial movement must be, which results in a strict constraining cycle.

Another known conveying device, which in particular uses plastic injection molding machines for preheating, Dosing, pressing, etc. is connected upstream, has a screw that one of the rotation has independent axial movement.

This possibility of movement is only provided so that the screw is in a channel (cylinder) can work against a closed mouthpiece, screwing back in the mass and in the Channel accumulates a batch of preheated material in front of the screw head. After reaching a certain pressure or volume should the screw then the whole in front of the screw head Eject the amount present. This conveyor device is therefore also not compatible with the screw extruder comparable according to the invention.

When carrying out the axial vibration of the screw according to the invention, in each case a good mass collection and a continuous mass transport enables. In addition, through the pulsation of the screw feeds additional energy into the mass to be processed in order to pass through it a rapid temperature increase of the plastic, even on the smallest mass particles and to create intimate plasticizing effects, which are essential for flawless, easy and clean melt management are essential to obtain strands of uniform high quality.

Another advantage is achieved with the invention that the stepless within wide limits adjustable amplitudes and frequencies a fine differentiation and dosage of the fed Shear heat allow to the particular physical properties of each to be processed Mass to be able to fully meet. Through these pulsating axial movements that are independent of the speed all mass particles in the cylinder become different from one another via the screw at the same time different directions and speeds imposed, the shear effects of which are higher, than could be achieved with known devices.

With the screw extruder according to the invention, it is possible to produce high molecular masses that in extrusion presses of known design only crumbly, so in unusable condition from the Nozzle entered without difficulty and strands in good plastic condition with satisfactory To maintain performance. Other masses that have so far been found to be difficult to deform on the one hand and within the known processing machines proved to be thermally endangered on the other hand, could considerably are more easily deformed and were much less thermally endangered.

Based on the drawing, the invention is intended to go through

such an embodiment will be explained in more detail.

The worm 1 is set in rotation by the motor 2 via the variable-speed gear 3 and thereby plasticized (for example with the help of the external cylinder heating system, not shown) the plastic mass falling from the hopper 4. Because of the constant rotation the screw 1 located in the plasticizing cylinder 5 is the plastic mass over the The screw head 6 is conveyed away through the nozzle 7 or another special tool.

According to the present invention, a pulsating axial movement (vibration) is now superimposed on the rotary movement of the screw 1, which z. B. can be brought about by a mechanical, pneumatic, hydraulic or other type of drive device. In the drawing, a pressure cylinder 8 is shown as an exemplary embodiment, in which the pulsating axial movement is generated by alternately acting on the piston 9. The maximum amplitude α is determined by the greatest stroke movement of the axial drive and can be set continuously down to zero. Analogously, it is also possible to regulate the frequency of the axial movement steplessly.

Claims (1)

Claim: Screw extrusion press for processing thermoplastics or similar Masses with one for the purpose of continuous conveying, plasticizing and ejecting rotatable screw, characterized by one of the screws independent of their rotational movement a pulsating axial movement (axial vibration) imposing drive device which is adjustable so that the frequency and amplitude of this axial movement to the respective conditions of the extrusion plant are adaptable. Considered publications:
German patent specifications No. 944 727, 909 395,
858 310, 1039 219; Patent Specification No. 6262 of the Office for Invention and Patents in the Soviet Zone of Occupation in Germany;
Swiss patent specification No. 247 704. 1 sheet of drawings